The claimed invention relates generally to the field of pouring multiple section concrete slabs. More particularly, the invention relates to an apparatus for accurately positioning dowels within a slab to distribute and equalize loads at the junctions between adjacent sections of the slab.
In the construction of concrete slabs, it has long been the practice to use forms to define the area into which the concrete slab is to be poured. The forms serve to contain the wet concrete mixture when it is poured and while it hardens. When a large slab is to be poured, wooden forms are commonly used to divide the slab into smaller subsections, each of which is poured separately. However, one problem that can arise when slabs are poured in separate subsections is that the junctions or joints between adjacent sections are subject to damage from downward forces exerted against the slab.
To reduce the effects of such forces, it is common practice to embed dowels into the slab. The dowels bridge across the joint between adjacent subsections of the slab and extend a short distance into each subsection. The dowels, which are typically two to four feet in length, are placed at regular intervals along the joint, and act to equalize and transfer loads that are exerted against the joint. Before the first section of the slab is poured, holes are drilled through the wooden forms at regular intervals. A dowel is then extended into each hole, so that approximately half of the dowel's length extends into the region where the slab is to be poured. The slab section is then poured into place, with the wet concrete surrounding the portion of each dowel that extends into the region where the concrete was poured. When the concrete has dried, the form is removed by slipping it off of the dowels, which remain embedded in the concrete. The adjacent slab section is then poured into place against the first section, over the remaining exposed portions of the dowels.
However, if the dowels are not installed correctly, problems can arise. Specifically, if the dowels are not parallel to the slab surface and perpendicular to the joint between the slab sections, unwanted stresses can be created in the slab, which can lead to cracking of the slab. Proper alignment of the dowels is made difficult by the fact that the hole in the form through which the dowel is inserted must have a substantially greater diameter than that of the dowel, to allow the form to be stripped off of the dowel once the first slab section has dried.
Heretofore, procedures for aligning the dowels have failed to provide consistent, proper placement of the dowels. In the field, workers typically nail shims or boards onto the outer surface of the form to support the dowels in place. However, the alignment is typically not precise, or consistent from dowel to dowel. Moreover, the positioning of the dowels can be easily disrupted by the wet concrete as it moves into place around the dowels.
A need therefore exists for a way to provide consistent, proper alignment of dowels. The alignment of the dowels should, however, be simple and straightforward, and should not interfere with the ability to strip the forms off of the dowels once the first section of the slab has dried.
It is therefore an object of the invention to provide an apparatus that will allow dowels to be properly and consistently aligned before and during the pouring of a concrete slab.
It is a further object of the invention to provide an apparatus that can be easily used by unskilled laborers, with a minimum of training.
It is a further object of the invention to provide an apparatus for aligning dowels that is low in cost, and does not require any special tools.